Description
Initially found this post on reddit (How to make sodium citrate):
I’ve noticed a few times over the past couple of days that people have been asking where to get Sodium Citrate. Short answer is online. Easiest and cheapest. However there maybe instances due to timing etc, where you may not be able to purchase it on line in time for your need. I did a bit of research a bit back and found out that you can make sodium citrate from baking soda (sodium bicarbonate) and Citric Acid, both of which should be readily available at your local grocer. For every 2.1 g of citric acid, use 2.5 g of sodium bicarbonate and if everything goes well, you’ll get 2.9 g of sodium citrate after evaporating all the water. Just mix the two ingredients with which ever liquid you’re using (milk or water) and you should be good to go, clearly no need to evaporate the water. e.g. for the Modernist Cuisine at Home it calls for 11g of Sodium Citrate, so you’d need ~8g (7.96) of Citric Acid and ~9.5g(9.48) to get 11g of Sodium Citrate. I have yet to try this but it seems like it should work. Just chemistry.
Then went digging some more and eventually ended up on this forum (link):
Basic recipe: if you want 100.0 grams of sodium citrate, then you’ll need 85.69 grams sodium bicarbonate (i.e., baking soda) and 71.45 grams citric acid (which I assume is monohydrate; if you know you have anhydrous citric acid, use 65.33 grams instead) and dissolve them both in water. There will be lots of CO2 bubbles released so you may want to add things in slowly.
If you are making the sodium citrate for immediate use, then it’s usually easy enough to just add 85.7% baking soda and 71.5% citric acid to your cooking liquid in place of 100% sodium citrate and continue with your recipe. I wouldn’t recommend doing this directly in milk (use some water/beer instead and add the milk later) since the bubbles will foam the milk up and get unruly. This reaction technically adds a bit of water as well (12.25% of the sodium citrate weight) but this is usually < 0.8% of the total liquid in the recipe assuming the usual concentrations of sodium citrate so is likely negligible.
If you want a powder for later, you just need to boil the water off. To get the dihydrate form, keep the solution below 158 C/316 F. Putting it in the oven at around 300 F should work. Breaking it up periodically as it is drying can help to get a powder in the end.
I ended up using the bottom recipe. I made one batch with the sodium carbonate and one with the baking soda, the baking soda one came out better, but I think I didn’t fully dissolve the sodium carbonate one. We ended up using mostly the baking soda one and then added the sodium carbonate to get enough for the recipe
Ingredients
- 12.855g baking soda (also used sodium carbonate aka washing soda, see notes)
- 10.725g citric acid
- Water
Method
- Set an oven (toaster oven is great) for 300 degrees, convection if you’ve got it
- Combine the soda and acid crystals in a non reactive (glass) bowl
- Add water little by little until everything is wet and reacting. The more water you add the longer it will take to evaporate it. But add too little water and the reaction won’t complete. Recommend adding water and stirring until the reaction stops, and then adding more water and seeing if the reaction continues. I had a stir plate that I made for homebrewing, so I put a stirring bar in the bow and let the stir plate do the work
- Once the solution is no longer reacting (and is completely dissolved), place the bowl in the oven and bake until the water is evaporated. With a well dissolved solution it should basically precipitate all at once. If there are chunks that aren’t completely dry, try crushing them and bake until completely dry.
- Grind with mortal and pesstle